(A) Field of the Invention
This invention relates to refractory fiber articles and their method of manufacture and more particularly relates to refractory fiber articles comprising refractory fibers bound together with a refractory cement and to the method of manufacturing such articles. The invention further relates to the refractory cements and compositions utilized to bind the refractory fibers.
(B) History of the Prior Art
In the prior art is is known that certain refractory fibers can be held together with certain refractory cements. For example, it is known that alumino-silicate fibers can be bound together with compositions comprising a high percentage of colloidal silica. The use of colloidal silica, unfortunately, has had certain disadvantages in that the colloidal silica is costly and is not as temperature resistant as the alumina containing fibers which the colloidal silica binder holds together.
It was, nevertheless, felt necessary that colloidal silica be used in binder compositions to hold alumina containing fibers together. The use of the colloidal silica in conjunction with other additives was believed necessary in order to obtain an inorganic binder system which would not migrate during drying of the composition. It is stated, for example, in U.S. Pat. No. 3,775,141 issued Nov. 27, 1973 to Weidman that 10% to 200% by weight negatively charged colloidal silica impregnant is used and preferably 30% to 150% impregnant is used in conjunction with other additives to minimize migration of the colloids.
In the absence of colloidal silica plus aluminum chlorhydrate, or other aluminum salt, to prevent binder migration, flocculants or other compounds were believed necessary to cause the actual binding material in the binder composition to deposit upon the surface of the fibers. Such flocculants are described in the previously mentioned U.S. Pat. No. 3,775,141 and in U.S. Pat. No. 3,785,838 issued Jan. 15, 1974 to Weidman. Neither of these patents disclose a binder composition which will result in an entirely alumina based binder holding alumina or alumino-silicate fibers.
In the prior art it was known that refractory cements could be prepared which consisted essentially of alumina or alumina forming compounds. These cements were used, for example, in the construction of furnaces or for repairing furnaces or parts of furnaces as well as for embedding or cementing nozzles and the like shapes into metal housings to protect the housings from the effect of high temperature and erosion, or for use as a mortar in laying refractory bricks and for similar objects. Such compositions are described in U.S. Pats. Nos. 2,818,345 issued Dec. 31, 1957 to Vickers et al. and 3,274,008 issued Sept. 20, 1966 to Braunwarth et al. Neither of these patents describe any method for gelling or thickening an entirely alumina forming binder composition to prevent binder migration nor do either of the patents describe the binding of alumina or alumino-silicate fibers with a binder composition which will form an entirely alumina based binder.